1. Field
The disclosure relates to techniques for dynamic power management.
2. Description of the Related Art
In a conventional system, a server that operates as a data center is connected to a storage subsystem. Power delivery and cooling capability in datacenters is limited. Improving this capability is technically challenging and expensive. Storage subsystems are responsible for a large portion of the power consumption and the heat load. For example, in many cases the storage subsystem includes disk drives, and power is used to keep a disk drive available for reads and writes (i.e., “awake”) even when there are no existing reads and writes for the disk drive. Additionally, when disk drives are moved to a reduced power state, moving the disk drives to a higher powered state is sometimes time consuming.
Another problem in conventional systems is lowered availability in data centers due to failures in power and cooling systems. In a data center, power delivery (e.g., utility power, UPS, backup generators) and cooling systems occasionally break down. Today, many data centers are shut down while working through such failures. In order to maintain high availability, it is important that data centers continue to operate.
Conventional storage subsystems have hardly any form of power management. Typically, logic on each drive of a storage subsystem manages the local drive, which may include spinning down during periods in which the local drive is not busy. However, there is a fear in that putting the storage subsystem into a low-power state has a deleterious effect on I/O throughput, thus compromising On-Line Transaction Processing (OLTP) results.
Thus, either disk drives have power management implemented at the drive level where drives spin down when the load is less or device power states are not actively managed, so that disk subsystems are left running continuously.
Therefore, there is a need in the art for improved power management of storage subsystems.